This invention relates to a process for the removal of iron contamination from zirconiferous materials, particularly the removal of iron oxide coatings from zircon grains. It is to be understood that the terms "iron oxide coatings" and "iron oxide", used herein include iron oxide and/or iron hydroxides and/or compounds of both iron oxide and/or iron hydroxides and in both amorphous and crystalline forms. It will also be understood that this specification adopts the convention of expressing iron oxide content as equivalent Fe.sub.2 O.sub.3 content by weight.
Zircon (ZrSiO.sub.4) is a major component of most so-called "mineral sands" or "heavy mineral" deposits along with titanium-bearing minerals ilmenite and rutile as well as small amounts of other minerals such as monazite. Zircon finds major uses in foundries, refractories, abrasives and ceramic glazes and enamels.
Zircon is extracted from mineral sands deposits by mining followed by wet concentration to remove coarse and fine sands and slimes to produce a heavy mineral concentrate. The concentrate is subjected to various combinations of gravity separation, magnetic separation and electrostatic separation to yield separate streams of zircon, ilmenite, rutile and monazite.
Depending largely on the particular mineral sands orebody or section of the orebody and to a minor extent on the methods of concentrate separation employed, the zircon grains are coated to varying degrees with iron oxide(s). In many instances, the iron oxide contamination is such that the zircon is unsuitable for certain end-use applications, especially where colour is a criterion, for example for use in ceramic glazes and enamels. Such "ceramic grade zircon" must typically contain a maximum of 0.07% by weight iron oxides expressed as Fe.sub.2 O.sub.3.